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Title: Thermal conductivity of cementitious grouts and impact on heat exchanger length design for ground source heat pumps

Abstract

Design length and performance of heat exchangers for ground source heat pumps strongly depend on the thermal conductivity of the backfill material. Laboratory studies were undertaken to determine means of improving thermal conductivity of cementitious backfill grouts. The influence of fillers and admixtures was examined. Significant improvement of grout thermal conductivity was readily achieved through appropriate materials selection and mix design. Fillers such as silica sand, alumina grit, steel grit, and silicon carbide increased the thermal conductivity to values ranging from 1.7 to 3.3 W/(m{center_dot}K). Neat cement grouts had conductivities of 0.80 to 0.87 W(m{center_dot}K). Filled cementitious grouts had better retention of thermal conductivity under drying conditions than bentonites and neat cements. The reduction in required bore length possible with cement-sand grouts was predicted theoretically for an example heat pump system and found to be 22 to 37%, depending on soil conductivity and bore diameter.

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Lab., Upton, NY (US)
OSTI Identifier:
20104797
Resource Type:
Conference
Resource Relation:
Conference: ASHRAE Winter Meeting, Dallas, TX (US), 02/05/2000--02/09/2000; Other Information: The full text of this paper can be found in the International Journal of Heating, Ventilating, Air-Conditioning and Refrigerating Research; 5: No.2, 85-96(Apr 1999); PBD: 2000; Related Information: In: ASHRAE Transactions 2000; Volume 106, Part 1, 929 pages.
Country of Publication:
United States
Language:
English
Subject:
15 GEOTHERMAL ENERGY; GROUND SOURCE HEAT PUMPS; DESIGN; HEAT EXCHANGERS; LENGTH; SEALING MATERIALS; THERMAL CONDUCTIVITY; PERFORMANCE; BACKFILLING; GROUTING; FILLERS; BOREHOLES

Citation Formats

Allan, M L, and Kavanaugh, S P. Thermal conductivity of cementitious grouts and impact on heat exchanger length design for ground source heat pumps. United States: N. p., 2000. Web.
Allan, M L, & Kavanaugh, S P. Thermal conductivity of cementitious grouts and impact on heat exchanger length design for ground source heat pumps. United States.
Allan, M L, and Kavanaugh, S P. 2000. "Thermal conductivity of cementitious grouts and impact on heat exchanger length design for ground source heat pumps". United States.
@article{osti_20104797,
title = {Thermal conductivity of cementitious grouts and impact on heat exchanger length design for ground source heat pumps},
author = {Allan, M L and Kavanaugh, S P},
abstractNote = {Design length and performance of heat exchangers for ground source heat pumps strongly depend on the thermal conductivity of the backfill material. Laboratory studies were undertaken to determine means of improving thermal conductivity of cementitious backfill grouts. The influence of fillers and admixtures was examined. Significant improvement of grout thermal conductivity was readily achieved through appropriate materials selection and mix design. Fillers such as silica sand, alumina grit, steel grit, and silicon carbide increased the thermal conductivity to values ranging from 1.7 to 3.3 W/(m{center_dot}K). Neat cement grouts had conductivities of 0.80 to 0.87 W(m{center_dot}K). Filled cementitious grouts had better retention of thermal conductivity under drying conditions than bentonites and neat cements. The reduction in required bore length possible with cement-sand grouts was predicted theoretically for an example heat pump system and found to be 22 to 37%, depending on soil conductivity and bore diameter.},
doi = {},
url = {https://www.osti.gov/biblio/20104797}, journal = {},
number = ,
volume = ,
place = {United States},
year = {2000},
month = {7}
}

Conference:
Other availability
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